Global food demand is projected to rise by 50-60% by 2050, necessitating agricultural intensification and placing greater pressure on water resources, particularly in arid regions. This study investigates the relationship between cropland expansion and groundwater irrigation in the Hexi Corridor, a critical agricultural and ecological zone in northwestern China, from 2000 to 2022. We integrate multi-source remote sensing data (CLCD, MOD16, Landsat 8-9) with ground-based well records to quantify the spatiotemporal patterns of croplands, irrigation water demand, and well development. Results indicate that the cropland area expanded at 0.77% per year, with groundwater serving as a primary irrigation source in 82.9% of villages. Evapotranspiration increased significantly (4.87 mm/yr), driving higher water demand. Well construction was strongly correlated with cropland expansion, with each new well supporting 0.27 km2 of cropland. Wells were progressively constructed farther from rivers (4.3 m/yr), reflecting growing dependence on groundwater. Areas with regularly distributed wells exhibited 23% higher vegetation indices, suggesting enhanced water-use efficiency. Despite these gains, unsustainable trends emerged, and groundwater overexploitation in the Shule and Heihe River basins was observed, mirroring past crises in the now-recovering Shiyang River basin. Policy interventions implemented after 2014 slowed expansion of agricultural water use or cropland, but failed to fully decouple agricultural growth from water depletion completely. We propose a spatially differentiated groundwater management framework, integrating well density and proximity to rivers, to balance agricultural and ecological water needs. These findings highlight the risks of groundwater-driven agricultural expansion in arid regions and underscore the need for infrastructure planning aligned with hydrological limits.